Microbiology · Streptococci and enterococci
Enterococcus !
- Bacterium
- Gram-positive
- Contact
- Exam priority: medium
Gut cocci that cause urinary infection, endocarditis and hospital infections; some strains resist vancomycin (VRE).
Updated 2026-11-01
Also called: Enterococcus faecalis, Enterococcus faecium, VRE (vancomycin-resistant enterococcus)
At a glance
- Gram
- Gram-positive
- Shape
- Cocci in pairs and short chains
- Oxygen
- Facultative anaerobe
- Family
- Enterococcaceae
- Stain
- Gram positive; catalase negative; PYR positive
Morphology
- Gram-positive cocci in pairs or chains
- Grows on bile esculin and in 6.5 % NaCl
- Gamma or variable haemolysis
Transmission
- The patient's own gut flora
- In hospital: contaminated hands, surfaces and equipment
- VRE does not spread through the air
Isolation precautions
What the care team adds to standard precautions.
- Contact
- Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.
Virulence factors
- Intrinsic resistance to cephalosporins
- Acquired vancomycin resistance (van genes: D-Ala-D-Lac)
- Biofilm on urinary catheters
Diseases it causes
- Urinary tract infection, especially with a catheter Urinary tract infection (acute cystitis) →
- Infective endocarditis (E. faecalis) Infective endocarditis →
Clinical picture
- Catheter-associated urinary infection
- Bacteraemia in hospitalised patients
- Subacute endocarditis in older adults, sometimes after urological or bowel procedures
Diagnosis
- Culture: growth on bile esculin and in 6.5 % NaCl
- PYR positive
- Susceptibility testing to ampicillin and vancomycin
Treatment
Ampicillin is preferred for susceptible E. faecalis; in endocarditis it is combined with an aminoglycoside or with ceftriaxone. E. faecium is often ampicillin resistant. VRE is treated with linezolid or daptomycin. Cephalosporins never cover enterococci.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Hand hygiene
- Contact precautions for patients with VRE
- Antibiotic stewardship
- Removing unneeded catheters
Test yourself
Think of the answer, then tap the question to see it.
Why do cephalosporins fail against enterococci?
Intrinsic resistance: their PBPs have low affinity for cephalosporins.
Which molecular change makes enterococci vancomycin resistant?
The peptidoglycan end changes from D-Ala-D-Ala to D-Ala-D-Lac, which vancomycin binds poorly.
Which precautions does a patient with VRE need?
Standard precautions plus contact precautions.
Which two growth tests identify enterococci?
Growth on bile esculin agar (which it hydrolyses) and in broth with 6.5 % NaCl.
Related
Related conditions
← Back to the group: Streptococci and enterococci
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Vancomycin-resistant Enterococci (VRE) Basics (CDC, 2024); Endocarditis: MedlinePlus Medical Encyclopedia (MedlinePlus (NLM), 2024); Urinary tract infection - adults (MedlinePlus (NLM), 2024).
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Representative model, for educational purposes only.